Dangerfield has fallen off contract with Adelaide, but having been on the Crows' list for eight seasons, is categorised as a restricted free agent.

That means the Crows are entitled to match Geelong's offer - but no other club in AFL history has opted to match a free agency offer.

Adelaide is believed to favour matching Geelong's offer, which would then force the Cats to strike a trade deal.

If the Crows opt not to match the offer, compensation for Dangerfield would be decided by the AFL and likely be a first-round draft selection which Adelaide deem unsuitable compensation for losing the three-time All Australian.

The other option, considered most unlikely, is that Dangerfield nominates for the pre-season draft, stating he wants to play for Geelong and no one else, and nominates his salary.

But that scenario is high-risk as other clubs with pre-season draft selections before Geelong could call his bluff and match the salary offer.